如何使用起始编号和结束编号列出文件系统中可用的文件？
就像500中有C:\Test\个文件一样，如何列出从1到20开始的文件，如
根据此列表给出start number and end number可用于特定文件路径的文件。
我在java中尝试这个
我试过这样的事情，它给了我给定路径的所有可用文件
public static List<String> loadAllFiles(String filesLocation) {
//find OS
//String osName = System.getProperty("os.name");
//replace file path based on OS
filesLocation = filesLocation.replaceAll("\\\\|/", "\\"+System.getProperty("file.separator"));
List<String> pdfFiles = new ArrayList<String>();
if (log.isDebugEnabled()) {
log.debug("In loadAllFiles execute start");
}
File directoryList = new File(filesLocation);
File[] filesList = directoryList.listFiles();
try {
for (int count = 0; count < filesList.length; count++) {
if (!filesList[count].isDirectory() && filesList[count].getName().endsWith(SPLIT_AND_SAVE_WORKING_FILE_EXTENSION.trim())) {
// load only PDF files
pdfFiles.add(filesList[count].getName().replace(SPLIT_AND_SAVE_WORKING_FILE_EXTENSION.trim(), ""));
}
}
} catch (Exception filesException) {
filesException.printStackTrace();
//TODO : Log the exception
} finally {
if (filesList != null)
filesList = null;
if (directoryList != null)
directoryList = null;
}
log.debug("In loadAllFiles execute end");
return pdfFiles;
}
I think the question is misunderstood, Say if i have 1000 files[file names can be anything] and i want to restrict getting the files name like i will give starting Number and ending number. like 1 to 20 and i want to load those 20 files alone.
答案 0 :(得分：8)
没有使用普通Java 7的外部库的示例
import java.io.IOException;
import java.nio.file.DirectoryStream;
import static java.nio.file.DirectoryStream.Filter;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
// list files starting with 1 till 20 "-.*"
public class FileNameFilter {
private static final Filter<Path> fileNameFilter = new Filter<Path>() {
@Override
public boolean accept(Path entry) throws IOException {
if (!Files.isRegularFile(entry)) {
return false;
}
return entry.getFileName().toString().matches("^([1][0-9]{0,1}|2[0]{0,1})-.*");
}
};
public static void main(String[] args) {
final String filesLocation = "resources/";
Path path = Paths.get(filesLocation);
try (DirectoryStream<Path> dirStream = Files.newDirectoryStream(path, fileNameFilter)) {
for (Path entry : dirStream) {
System.out.printf("%-5s: %s%n", "entry", entry.getFileName());
}
} catch (IOException e) {
// add your exception handling here
e.printStackTrace(System.err);
}
}
}
修改 Java 8版本
// list files starting with 1 till 20 "-.*"
public class FileNameFilter {
public static void main(String[] args) {
final String filesLocation = "resources/";
try {
Files.walk(Paths.get(filesLocation))
.filter(p -> p.getFileName().toString().matches("^([1][0-9]{0,1}|2[0]{0,1})-.*"))
.forEach(entry -> {System.out.printf("%-5s: %s%n", "entry", entry.getFileName());});
} catch (IOException e) {
// add your exception handling here
e.printStackTrace(System.err);
}
}
}
编辑2
列出目录中前20个文件的示例
note 文件的顺序与您在目录中运行ls或dir的顺序相同。
Java 7示例
import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class FileListLimiter {
private static final int MAX_FILES_TO_LIST = 20;
public static void main(String[] args) {
final String filesLocation = "resources/";
Path path = Paths.get(filesLocation);
try (DirectoryStream<Path> dirStream = Files.newDirectoryStream(path)) {
int fileCounter = 1;
for (Path entry : dirStream) {
System.out.printf("%-5s %2d: %s%n", "entry", fileCounter++, entry.getFileName());
if (fileCounter > MAX_FILES_TO_LIST) {
break;
}
}
} catch (IOException e) {
// add your exception handling here
e.printStackTrace(System.err);
}
}
}
Java 8示例
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
public class FileListLimiter {
private static final int MAX_FILES_TO_LIST = 20;
public static void main(String[] args) {
final String filesLocation = "resources/";
try {
Files.walk(Paths.get(filesLocation))
.filter(p -> p.toFile().isFile())
.limit(MAX_FILES_TO_LIST)
.forEach(entry -> {System.out.printf("%-5s: %s%n", "entry", entry.getFileName());});
} catch (IOException e) {
// add your exception handling here
e.printStackTrace(System.err);
}
}
}
答案 1 :(得分：1)
尝试类似
的内容final String pattern = "^[1-20].*";
final FileFilter filter = new RegexFileFilter(pattern);
final File[] files = directory.listFiles(filter);
答案 2 :(得分：1)
为什么不使用这个逻辑。它很直接，你不需要任何替换或替换。我认为你将能够很容易地将它转换成代码到Java。我没有测试正则表达式，但你得到了基本的想法。
1.使用扫描仪（或任何其他方式）获取开始和结束限制的输入范围。
2.创建目录列表，扫描目录中的每个文件。在这里使用for循环。
3.定义正则表达式以仅获取文件的起始数据。
start pattern = (^[0-9]{0,2})[a-zA-Z].+[0-9]{0,2}$ use grouping in regular expression to fetch this group1
4.如果从group1获取值，请检查文件名是否以group1数据开头。
5如果此数据介于您要搜索的范围之间，则创建一个arraylist并将匹配的文件存储在arraylist中。
6.继续进行直到目录结束。最终的arraylist将包含给定范围内的文件。
希望这会有所帮助
答案 3 :(得分：1)
从Java 7开始，您可以利用Files#walkFileTree。在visitFile期间，您可以使用正则表达式查找特定文件。
像这样的东西
Path start = Paths.get(filesLocation);
Final Pattern pattern = Pattern.compile("^([1]?[0-9]|[2][0])\\.pdf");
Files.walkFileTree(start, new SimpleFileVisitor<>()
{
@Override
public FileVisitResult visitFile(Path filePath, BasicFileAttributes attrs)
throws IOException
{
File f = filePath.toFile();
if (pattern.matcher().matches(f.getName())) {
System.out.println("Valid match found " + f.getName())
}
return FileVisitResult.CONTINUE;
}
});
答案 4 :(得分：1)
我不确定我是否完全理解您的问题，但这是一个Java 8示例，它迭代按名称排序的目录文件，从给定的偏移量开始并将结果限制为给定的大小。它还允许您从结果中包含/排除目录。
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Collection;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class DirectoryWalkerTest {
public static void main(final String... args) throws IOException {
final String filesLocation = "/path/to/files";
System.out.println(getFiles(filesLocation, true, 0, 10));
System.out.println(getFiles(filesLocation, true, 10, 10));
System.out.println(getFiles(filesLocation, false, 0, 10));
System.out.println(getFiles(filesLocation, false, 10, 10));
}
/**
* Returns a limited list of filenames starting at the given offset.
*
* @param filesLocation the directory to scan
* @param filterDirectories should we include directories in results
* @param offset the starting offset
* @param limit the maximum number of results
* @return a collection of file names
*/
private static Collection<String> getFiles(final String filesLocation, final boolean filterDirectories,
final int offset, final int limit) throws IOException {
Stream<Path> stream = Files.list(Paths.get(filesLocation));
if (filterDirectories) {
stream = stream.filter(path -> !Files.isDirectory(path));
}
return stream
.map(Path::toString)
.sorted()
.skip(offset)
.limit(limit)
.collect(Collectors.toList());
}
}
答案 5 :(得分：1)
根据您的代码，您可以尝试：
int begin = 0;
int limit = 10;
for (int count = 0; count < filesList.length; count++)
{
if (!filesList[count].isDirectory() && filesList[count].getName().endsWith(SPLIT_AND_SAVE_WORKING_FILE_EXTENSION.trim()))
{
// moving to begin index, only if the file is not a directory and is matching your criteria, whatever it is
if (count < begin) continue;
// load only PDF files
pdfFiles.add(filesList[count].getName().replace(SPLIT_AND_SAVE_WORKING_FILE_EXTENSION.trim(), ""));
}
// Stopping when limit is reached
if (pdfFiles.size() == limit) break;
}
根据您的条件，它将移至begin索引并获取limit个项目。
答案 6 :(得分：1)
我玩弄它并提出了适合我的东西。也许你可以找到你需要的部件。如果您不想要完整路径，只需删除getCanonicalPath（）。
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
public class GetFirst_20_pdf_files {
// Creating an empty array list with 10 entries (the default)
ArrayList<String> pdfFiles = new ArrayList<String>();
public ArrayList<String> myList() {
// here you can get start and end from user
int start = 2;
int end = 4;
// and set the directory
String filesLocation = ".";
File directoryList = new File(filesLocation);
File[] files = directoryList.listFiles();
int count = 0;
for (File file : files) {
// don't want directories
if (file.isDirectory()) { continue; }
// want ".pdf" files only
if (!file.getName().toLowerCase().endsWith(".pdf")) { continue; }
// only want between start and end
count++;
if (count >= start && count <= end) {
try {
pdfFiles.add(file.getCanonicalPath());
} catch (IOException e) {
System.out.println(e);
}
if (count >= end) { return pdfFiles; }
}
}
return pdfFiles;
}
public static void main(String[] args) throws IOException {
GetFirst_20_pdf_files L = new GetFirst_20_pdf_files();
ArrayList<String> aList = L.myList();
for (String p : aList) {
System.out.println(p);
}
}
}